javascript strange rounding problem

Question

I have the following javascript function for rounding:

function round(val, numberdigits){ return Math.round(val*Math.pow(10, numberdigits))/Math.pow(10, numberdigits); }

In most of the cases, it does its job well, but in some rare cases, the returned value has one digit more, which is always a 5.

Example list of results with numberofdigits = 3:

5.329 - 5.081 - 4.271 - 3.271 - 2.1525 - 2.1375 - 2.1225 - 1.997 - 2.044 - 2.031 - 2.028

Can someone explain this? Or maybe provide me with a better rounding function which prevents this problem?

James Wheare · Accepted Answer · 2009-08-26 15:33:09Z

1

You can use the built-in toFixed method on Numbers:

Number(val.toFixed(numberofDigits))

answered Aug 26, 2009 at 9:43

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1 Comment

If you care for the type of the value then you need to be aware that .toFixed returns string so you may want to wrap it in Number().